The present invention relates in general to an automatic washing machine, and more particularly to an automatic washing machine capable of selective power transmission from a drive motor to a washing and dehydrating tub in order to automatically convert its mode between the washing mode and the dehydrating mode.
As well known to those skilled in the art, a conventional automatic washing machine includes a drive motor and a clutch which are placed at the outside of the lower section of an outer tub and connected to each other by a transmission V-belt. The washing machine also includes a washing shaft and a dehydrating shaft either of which is applied with the rotational force of the drive motor under the clutching operation of the clutch to be rotated, thus to achieve a desired washing operation or a desired dehydrating operation.
With reference to FIG. 1, there is shown in a schematic view an example of the conventional automatic washing machine. The washing machine includes an inner tub 22 which is placed in an outer tub 21 such that it is rotated by the rotational force of a drive motor 23.
Here, the drive motor 23 is placed at the outside of the lower section of the outer tub 21 and connected to a clutch assembly 26 by a transmission V-belt 24, which is wrapped about a motor pulley and a clutch pulley, as described above.
The automatic washing machine further includes two types of shafts, that is, a dehydrating shaft, which comprises upper and lower dehydrating shafts 29 and 31, and a washing shaft 37. The dehydrating shaft 29 and 31 and the washing shaft 37 coaxially extend from the clutch assembly 26 and are coupled to the inner tube 22 and a rotator 25, respectively. Here, the rotator 25 will be a pulsator or an agitator in accordance with the type of the washing machine.
FIG. 2 is an enlarged sectional view showing a construction of the clutch assembly 26. In this clutch assembly 26, a spring block 28 is fixed to a lower section of a gear shaft 27 and directly applied with the rotational force of the drive motor 23 through the V-belt 24.
A clutch spring 32 is mounted about the lower dehydrating shaft 31 which is integrally formed with both the upper dehydrating shaft 29 and a brake drum and gear housing 30. This clutch spring 32 controls the rotational force of the drive motor 23 transmitted to the clutch assembly 26 during the washing operation of the washing machine.
In order to apply a predetermined pressure to the outer surface of the brake drum and gear housing 30, a brake band 39 is wrapped about the brake drum and gear housing 30.
The clutch assembly 26 also includes a clutch boss 33 which is provided with teeth 33a at its circumferential surface and coupled to the outer surface of the clutch spring 32. In addition, a clutch boss cam 35 is rotatably mounted on a lower end of a brake lever 34.
The brake lever 34 is placed at a predetermined position where it is engaged with the teeth 33a of the clutch boss 33 and cooperates with a drain valve operating solenoid (not shown) which is mounted on a side of the outer tub 21.
In order to prevent reverse rotation of the inner tub 22, the clutch assembly 26 includes an one way spring clutch 36.
A planet gear 38 is provided in the clutch assembly 26 for reduction of the rotational force of the gear shaft 27 prior to transmission of this rotational force to the washing shaft 37.
In the case of the washing mode of this conventional automatic washing machine, the clutch is in a non-clutched state, so that only the rotator 25 is alternately rotated in opposed directions while the inner tub 22 is stopped. However, in the case of the dehydrating mode of the washing machine, the clutch is in a clutched state, so that the rotator 25 and the inner tub 22 are simultaneously rotated at the same high rotational speed.
Hereinbelow, the operations of the conventional washing machine in the washing mode and of the dehydrating mode will be described in detail.
In the washing mode of the washing machine, the forward rotational force of the drive motor 23 is transmitted to the clutch assembly 26 through the V-belt 24 wrapped about the clutch pulley. In this case, the clutch pulley is rotated in the forward direction and this forward rotation of the pulley tightens the clutch spring 32, thus to transmit the rotational force of the drive motor 23 to the lower dehydrating shaft 31 through the spring block 28.
However, the teeth 33a of the clutch boss 33 on the outer surface of the clutch spring 32 push the clutch boss cam 35 and prevent tightening of the clutch spring 32, thereby causing no rotational force of the motor 23 to be transmitted to the upper dehydrating shaft 29.
At this time, the rotational force of the motor 23 transmitted to the gear shaft 27 is reduced by the planet gear 38 and, thereafter, transmitted only to the washing shaft 34.
Only the rotator 25 coupled to the washing shaft 37 is thus rotated in order to achieve the desired washing operation.
Meanwhile, the reverse rotational force of the drive motor 23 in the washing mode is transmitted to the clutch assembly 26 through the V-belt 24 in the same manner as described for the above forward rotational force. In this case, the clutch pulley is rotated in the reverse direction and this loosens the clutch spring 32, causing the rotational force of the gear shaft 27 not to be transmitted to the dehydrating shaft 29 but to washing shaft 37 through the planet gear 38. At this time, the rotational force is reduced by the planet gear 38 prior to its transmission to the washing shaft 37.
When the rotational force of the gear shaft 27 is reduced by the planet gear 38, there is generated a reaction torque in the gear housing 30, so that the upper dehydrating shaft 29 may be rotated in reverse direction.
However, this reverse rotation of the dehydrating shaft 29 is reliably prevented by both the one way spring clutch 36 and the brake band 39 wrapped about the brake drum and gear housing 30.
In the dehydrating mode of the washing machine, the forward rotational force of the drive motor 23 is transmitted to the clutch assembly 26 through the V-belt 24 wrapped about the clutch pulley. In this case, the clutch pulley is rotated in the forward direction and this forward rotation of the pulley tightens the clutch spring 32, thus to turn on the drain valve operating solenoid (not shown) and to pull a lever 40.
The clutch spring 32 thus comes into close contact with the spring block 28, and the clutch boss cam 35 of the brake lever 34 cooperating with the lever 40 is separated from the teeth 33a of the clutch boss 33 and, at the same time, the brake band 39 is released from the outer surface of the gear housing 30. Therefore, the rotational force of the spring block 28 is transmitted to the lower dehydrating shaft 31 of the gear housing 30 and rotates the upper dehydrating shaft 29, integrally formed with the gear housing 30, at a high speed without speed reduction. The inner tub 22 and the rotator 25, which are coupled to the dehydrating shaft 29 and the washing shaft 37 respectively, are thus rotated at high speed, thereby achieving the desired dehydrating operation.
When the desired dehydration is finished or the dehydration mode of the washing machine is canceled, the drain valve operating solenoid is turned off.
Upon turning off the drain valve operating solenoid, the pulled lever 40 is released from its pulled state, and the clutch boss cam 25 is engaged with the teeth 33a of the clutch boss 33 and, at the same time, the brake band 39 is tightened on the outer surface of the gear housing 30, thus causing the washing machine to be converted in its mode into the washing mode. The rotation of the brake drum and gear housing 30 is thus stopped.
Accordingly, the inner tub 22 coupled to the dehydrating shaft 29 and to the gear housing 30 is stopped in order to end the operation of the washing machine.
As described above, the conventional automatic washing machine should have a complex clutch for selective transmission of the rotational force of the drive motor to the inner tub in accordance with the operational mode of the washing machine. Hence, the manufacturing cost of the washing machine is increased. In addition, the provision of the clutch assembly causes a power loss in selective transmission of the rotational force of the drive motor to the washing shaft or to the dehydrating shaft under the control of the clutch assembly.